The present invention is a method and catalyst structure for steam reforming of a hydrocarbon.
Steam reforming of hydrocarbons is commonly used for feedstock production for carbon-monoxide hydrogenation (Fischer-Tropsch synthesis), methanol synthesis and hydrogen production. Steam reforming is done commercially by flowing a mixture of steam and the hydrocarbon past a supported catalyst having an alumina support and a catalyst metal thereon, and reacting the mixture at a temperature from about 600xc2x0 C. to about 1000xc2x0 C., forming at least one product. Research has been done with the catalyst metal on a spinel support. Residence times are typically on the order of seconds and steam to carbon ratio greater than about 2.5. For steam to carbon ratio less than 2.5, catalyst activity is generally degraded after hours to days due to coke formation and the supported catalyst must be refreshed or replaced.
The rate of supported catalyst activity degradation has been reduced by use of excess steam (steam to carbon ratio greater than 2.5). Excess steam, however, requires excess thermal energy and results in large system pressure drop. Using less steam results in faster degradation of catalyst activity because of coking from the hydrocarbon(s).
Hence, there is a need for a method of steam reforming of a hydrocarbon that provides greater product yield and permits using less steam and maintaining catalytic activity of the catalyst.
The present invention includes an improvement to the existing method of steam reforming of hydrocarbon, wherein the improvement comprises:
the flowing is at a rate providing a residence time less than about 0.1 sec resulting in obtaining product formation yield or amount that is the same or greater compared to product formation at a longer residence time. Another improvement of the present invention is operation at a steam to carbon ratio that is substantially stoichiometric and maintaining activity of the supported catalyst.
The present invention also includes a catalyst structure for steam reforming of a hydrocarbon. The catalyst structure has
(a) a first porous structure with a first pore surface area and a first pore size of at least about 0.1 xcexcm;
(b) a porous interfacial layer that is a spinel with a second pore surface area and a second pore size less than the first pore size, the porous interfacial layer having a thickness less than 4 mm placed upon the first pore surface area;
(c) a steam reforming catalyst selected from the group consisting of rhodium, iridium, nickel, palladium, platinum, carbide of group Vlb and combinations thereof placed upon the second pore surface area.
It is an object of the present invention to provide a method of steam reforming of hydrogen with a residence time of less than about 0.1 sec.
It is an object of the present invention to provide a catalyst structure with a porous interfacial layer of spinel.
The subject matter of the present invention is particularly pointed out and distinctly claimed in the concluding portion of this specification. However, both the organization and method of operation, together with further advantages and objects thereof, may best be understood by reference to the following description taken in connection with accompanying drawings wherein like reference characters refer to like elements.